XmR Individuals Chart Formulas
The XmR (Individuals and Moving Range) Chart can help you evaluate a process when there is only one measurement and they are farther apart: monthly postage expense and so on.
Here are the formulas used to calculate both the Moving Range and Individuals chart in QI Macros.
Moving Range Chart formula
Individuals X Chart formula
k = number of data points
for n=2 observations (moving range is calculated from two samples, the present minus the previous value)
D4 = 3.267
D3 = 0
E2 = 2.660
Conforms with ANSI/ASQC B1, B2, B3 1996
QI Macros XmR Charts employ the Nelson Rule for Moving Range
"Any moving range (Ri) greater than 3.5*Rbar should be removed from the average moving range calculation."
In example below, point 20 (46.50) is greater than 3.5*11.14 (original Rbar), so it will be removed from Rbar Calculation which changes Rbar to 9.73 and UCL/LCL for both the X and R charts.
Source: Control Charts for Individual Measurements, Lloyd S. Nelson, Journal of Quality Technology, Vol. 14, No. 34, July 1982.
Process: Calculate, plot, and evaluate the range chart first. If it is "out of control," so is the process. If the range chart looks okay, then calculate, plot, and evaluate the X Chart.
- Create a XmR Individuals Chart in Excel using QI Macros
- XmR Individuals Chart Video
- XmR Individuals Chart Template in Excel
The XmR Individuals chart is just one of the tools included in the QI Macros SPC Software for Excel.
Why Choose QI Macros Over Other Control Chart Software?
- Only $299 USD - less with quantity discounts
- No annual subscription fees
- Free technical support
Easy to Use
- Works right in Excel
- Create a chart in seconds
- Easy to customize & share charts
Proven and Trusted
- More than 100,000 users
- In More than 80 countries
- Five Star CNET Rating - Virus free